Climate change will present the greatest threat to health this century, amplifying the risk of disease, malnutrition and homelessness through floods, drought and rising sea levels, a medical panel said on Thursday.

"Even the most conservative estimates are profoundly disturbing and demand action," said the report, compiled over a year by The Lancet medical journal and experts from the Institute for Global Health at University College London.

"Climate change is the biggest global health threat of the 21st century."

The commission drew much of its data from the landmark Fourth Assessment Report, issued in 2007 by the UN's Nobel-winning climate experts, the Intergovernment Panel on Climate Change (IPCC).

Changing weather patterns could widen the habitat of disease-bearing mosquitoes, bringing malaria and dengue to previously cold regions, while flooding in poor countries will be a boon for cholera and other water-borne diseases.

Indirect effects on health include malnutrition as a result of poor harvests; injury and death from storms; and vulnerability from migration, as populations flee swamped delta cities or civil unrest.